Revan: hero, traitor, conqueror, villain, savior. A Jedi who left Coruscant to defeat Mandalorians — and returned a disciple of the dark side, bent on destroying the Republic. The Jedi Council gave Revan his life back, but the price of redemption was high. His memories have been erased. All that’s left are nightmares—and deep, abiding fear.

What exactly happened beyond the Outer Rim? Revan can’t quite remember, yet can’t entirely forget. Somehow he stumbled across a terrible secret that threatens the very existence of the Republic. With no idea what it is, or how to stop it, Revan may very well fail, for he’s never faced a more powerful and diabolic enemy. But only death can stop him from trying.

The novel begins two years after the events of Star Wars: Knights of the Old Republic and begins with Revan living on Coruscant, now married to Bastila Shan, on the outs with the Jedi Order and experiencing horrible insomnia due to nightmare he believes are part of his forgotten past as the Sith LordDarth Revan. Desperate for information on his past he tries to get in contact with a former subordinate of his from the Mandalorian Wars named Meetra Surik (The Exile, the main character from Star Wars: Knights of the Old Republic II: The Sith Lords) but finds out that she had been dismissed from the Jedi Order and has left Republic space. A meeting with his old friend Canderous Ordo provides Revan with another chance to regain his memories; a group of Mandalorians are searching for the mask of Mandalore, the traditional leader of the Mandalorian peoples. The mask was taken by Revan after defeating Mandalore and hidden away to prevent the Mandalorians from regrouping and to break their spirits. Before leaving, he learns from Bastila that she is pregnant; despite her protests Revan convinces her to stay as he doesn't know how long he will be gone.

On the planetDromund Kaas and unbeknownst to the Republic, the Sith Empire has rebuilt itself after being driven away by the Republic thousands of years ago. A Sith Warrior named Scourge is caught up in a rivalry between members of the Sith'sDark Council and is eventually employed by Darth Nyriss to root out traitors and threats to her safety. Scourge carries out his duties, despite growing concerns that Nyriss is trying to have him killed. After earning Nyriss's trust, the Sith Master confides in Scourge her plan to overthrow the Emperor as she believes he is insane and will bring ruin to the Sith Empire. She takes Scourge to the Emperor's homeworld of Nathema, which he finds completely devoid of the Force. Nyriss explains that a thousand years ago, a Sith Lord impregnated a farmer's wife who gave birth to the Emperor. Known then as Lord Vitiate, he eventually killed his parents once the truth of his parentage was revealed and through violence and terror eventually drove out the ruling Sith Lord. After the Sith Empire lost their war against the Republic it was Lord Vitiate who picked up the pieces and held the Empire together. Scheming to obtain immortality, he and other Sith performed a ritual that killed every living thing on the planet (the other Sith included) and transferred their life energy to Vitiate. Nyriss fears that the Emperor plans to invade the Republic and risk the stability of the Empire as well as the well being of the remaining Sith species, who were mercilessly hunted down by the Jedi.

After locating Mandalore's mask, Revan learns of Nathema from a recording he left behind that told him that Mandalore the Ultimate was approached by Sith to attack the Republic. Upon arriving at Nathema, Revan's ship the Ebon Hawk is shot down and Revan is captured by Scourge and Nyriss. Revan's droid, T3-M4, manages to eventually repair the ship and head back towards Republic space.

The book then jumps forward four years, right after the events of the Dark Wars. Meetra Surik arrives at the home of Bastila Shan and with T3-M4 in tow to show Bastila a recording T3 made of Revan being abducted by Sith. Although jealous of the relationship Meetra and Revan had, she is relieved to hear that Meetra is set on retracing Revan's path and finding him. She arrives on Nathema and after searching through a municipal building learns of Dromund Kaas and sets out for the planet. Arriving on Dromund Kaas, she passes herself off as a mercenary and eventually makes contact with Scourge who, after seeing Nathema and talking with Revan, has agreed that the Emperor is a danger to the Sith and must be stopped. After leaking information to the Emperor that Nyriss was a traitor, the Emperor decides to purge the entire Dark Council and sets his personal army upon them. During the chaos Scourge and Meetra manage to free Revan from his cell. Meetra gives Revan the mask that he wore during the Mandalorian Wars; upon wearing the mask all of Revan's memories return to him. After the end of the Mandalorian Wars, Revan and his friend Malak went out in search of the Sith Empire, but due to their corruption during the war they were made succeptible to the Emperor's will and were converted to the Dark Side and sent back to weaken the Republic so the Sith Empire could return and take over. Meetra and Scourge are attacked by Nyriss, but before she can kill them Revan approaches them and effortlessly kills the Sith Lord by directing her force lightning burst back to her.

After resting and watching a message from Bastila and his son Vaner, the three set out to eliminate the Emperor. Scourge however is troubled by visions he cannot explain, of a Jedi Knight and the Emperor. The three fight their way into the Emperor's throne room and Revan engages him in combat. The Emperor is frighteningly powerful. Revan is then nearly electrocuted to death by the Emperor, and is only stopped when T3 sets the Emperor on fire with his flamethrower. The Emperor directs his lighting at T3, annihilating the small droid. This is the moment that Meetra and Scourge intervene. At this moment Scourge understands his vision; he is seeing the death of the Emperor at the hands of a Jedi Knight, but it is not Meetra nor Revan. Understanding what needs to be done, Scourge stabs Meetra in the back, killing her instantly. Scourge lies to the Emperor saying this was all a ruse to flush out every traitor in the Empire and Revan is placed in a suspension tank where he is constantly interrogated and tortured by the Emperor for information about the Republic; unknown to the Emperor is that Revan is able to slightly impose his will upon the Emperor and plans to slow down his planned invasion of the Republic as long as he can so Bastila and his son will never see war. Scourge is rewarded with the Emperor's gift of immortality.

The book concludes many decades later with an elderly Bastila conversing with her son. They talk of Revan, and Vaner wonders if his father would have been disappointed that he never joined the Jedi Order but went into politics instead. Bastila assures him that he did the right thing, and that despite not knowing Revan's fate she knows he succeeded because they were still alive and the darkness that Revan feared never came to pass. Bastila then goes to sleep, dreaming of her lost husband.